Extruder for a 3D printer



FIG. 1 is a front, top, right side perspective view of an extruder for a 3D printer according to the new design;

FIG. 2 is a right side elevational view thereof;

FIG. 3 is a left side elevational view thereof;

FIG. 4 is a front elevational view thereof; and,

FIG. 5 is a top plan view thereof.

The broken lines in the drawings illustrate portions of the extruder for a 3D printer and form no part of the claimed design. 

CLAIM The ornamental design for an extruder for a 3D printer, substantially as shown and described. 